1. Field of the Invention
The present invention relates generally to biocides. The present invention relates more particularly to biocidal mixtures of oxazolidine compounds and hydroxymethyl-substituted phosphorus compounds, and methods of using them.
2. Technical Background
Protecting water-based fluids (e.g., in injection and production systems) from microbial contamination is vital for the efficiency and success of any oil or natural gas production operation. Metabolic activity of microorganisms can cause microbiologically influenced corrosion (MIC) on metal surfaces of equipment and cause degradation of polymer additives. Biofilms formed by both aerobic and anaerobic bacteria can physically plug oil and gas pipelines and water purification systems, as well as reduce efficiency of pumps and heat transfer systems. Moreover, certain anaerobic bacteria, known as sulfate reducing bacteria, can reduce sulfate to produce hydrogen sulfide, which can sour oil and gas, corrode pipelines and storage tanks and cause deposits of iron sulfide. Microbial contamination can occur anywhere throughout the oil and natural gas field during oil and gas production operations. For example, although aerobic and anaerobic bacteria coexist in many environments, aerobic bacteria are more often found topside (i.e., near the surface) in injection water, produced water, and functional water-based fluids such as drilling muds, completion or workover fluids, stimulation fluids and fracturing fluids. Anaerobic bacteria, on the other hand, are most commonly found downhole (i.e., underground) in oil or gas reservoirs, near bore areas, in produced fluids, in deaeration towers, in transmission pipelines, and in the water bottoms of oil and gas storage tanks.
Biological contamination is a major complication in many other industrial processes and systems. Pulp and paper water, cooling water (e.g., in cooling towers), boiler water, industrial process water, ballast water, waste water, metalworking fluids, water-based slurry, ink and tape-joint compound, water-based household products and personal care products, latex, paint, coatings, and water purification and treatment systems and components thereof are all vulnerable to contamination by aerobic and anaerobic bacteria.